If you hear light scratching or scurrying inside a wall at night, you probably have mice using the wall cavity as a hallway or nest. They get in and out where pipes, wires, vents and cabinets leave gaps, often under the kitchen or bathroom sink, behind the stove or dishwasher, or at the water heater. You cannot trap them inside a closed wall. You trap them at those exits, find where they enter from outside, and seal both.
Here is how to confirm it, where to look in an El Paso house, and what to do.
Confirm it is mice
Mice are mostly active after dark, so most people notice them at night. Light, quick scratching or skittering points to mice. Heavier thumps and gnawing are more often rats. Check cabinets on both sides of the noisy wall for rice-size droppings, shredded paper or chewed packaging. Our rodent noises article helps tell the sounds apart.
Where mice get into wall spaces
The CDC's list of places to check inside a home lines up with what technicians find.
- Inside, under and behind kitchen cabinets
- Around the pipes that lead to water heaters and furnaces
- Around floor air vents and dryer vents
- Behind the stove, fridge and dishwasher, where pipes and cords pass through
- Outlet and switch boxes on exterior walls
From outside, mice reach the walls through gaps at the slab, cracks in stucco, utility entries and roof openings. In El Paso, the lines that run to a rooftop evaporative cooler are worth checking.
Trap at the exits
Put snap traps where mice leave the wall: inside the sink cabinet next to the pipe hole, behind appliances, along the wall nearest the noise. The CDC recommends snap traps set in a T against the wall with a small amount of peanut butter as bait, checked every day.
Avoid poison inside the house if you can. A mouse that eats bait can die inside the wall, and in El Paso heat the smell can be strong for a week or more. Texas also follows EPA rules that require consumer bait to be sold in or with a bait station, and the strongest baits are not sold at retail.
Seal the gaps
Sealing is what ends the problem. Mice need only a gap about the width of a pencil, a quarter inch, according to the CDC.
- Pack small gaps around pipes and wires with steel wool or copper mesh, then lock it in with caulk or foam.
- Cover larger holes with hardware cloth, sheet metal or cement. Extension guidance specifies 24-gauge hardware cloth with quarter-inch mesh for mice.
- Seal the outside entry point too, not only the inside gaps.
- Check door bottoms. Extension guidance says exterior door gaps should be no more than a quarter inch.
Steel wool rusts outdoors, so copper or stainless mesh lasts longer outside. Our hole size article compares materials.
When the noise does not stop
If scratching continues after a week or two of trapping and sealing, there is likely a second entry point or a nest deeper in the wall. A technician can trace it. If you smell something rotten, a mouse may have died inside. See our dead rodent smell article.
Common El Paso entry points into walls
From the outside, check these spots first: where the main water line and gas line enter the house, the hose bib, the conduit for an air conditioner or outdoor lights, cracks in stucco near the slab, the opening where cooler lines pass through the roof, and the gap where a garage wall meets the house wall. A flashlight and a pencil are all you need. If the pencil fits, a mouse can too.
Older homes in central El Paso and the valleys often have decades of patched plumbing and wiring openings. Newer homes can have gaps that were never sealed during construction. Either way, a rodent exclusion visit will map them.
Signs the mice are gone
The scratching stops, traps stay empty for a week, and no new droppings show up in cleaned cabinets. That matches the CDC's test for a finished job. Keep one or two traps set under the sink for another couple of weeks as a check.
Cleanup after mice in the walls
Clean droppings in cabinets and behind appliances with the CDC wet method: air the room out for 30 minutes, wear gloves, spray with bleach solution, wait 5 minutes, wipe and double-bag. Do not vacuum the cabinet floor. Replace shelf liners that have droppings on them.
Frequently asked questions
Will mice in the walls leave on their own?
Rarely. They have shelter and often food nearby. Trapping and sealing are what make them leave or end up caught.
Can I put bait inside the wall?
It is not a good idea. Mice that die in the wall cause odor, and bait in wall spaces is hard to control.
Do I need to cut open the wall?
Usually not. Mice come out at existing gaps, and that is where trapping and sealing happen.
How long until the noise stops?
Often within one to two weeks of trapping and sealing. Longer usually means another entry point.
Can mice in the walls damage wiring?
Mice gnaw on many materials, including wire insulation. If you suspect chewed wiring, have an electrician check it.
Sources
- CDC: How to seal up to prevent rodents
- CDC: How to trap up to remove rodents
- CDC: How to clean up after rodents
- Wildlife Damage Management, eXtension: Rodent exclusion methods
- Texas Department of Agriculture: Rodenticide rules